Display devices and methods for detecting user-intended touch input

ABSTRACT

Display devices and methods for detecting user-intended touch input are provided. An example display device includes a touch-sensitive display. Further, the display device includes an impact sensor attached to the touch-sensitive display and configured to generate a signal representative of an impact of the touch-sensitive display. The display device also includes a computing device configured to receive the signal. The computing device is also configured to detect a peak of the signal. Further, the computing device is configured to determine whether a rising edge of a magnitude of the peak detected signal meet predetermined criteria. The computing device is also configured to indicate detection of user-intended touch in response to determining that the predetermined criteria are met.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 13/477,027, filed May 21, 2012; the entire contentof which is incorporated herein by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to display devices, and more specifically,to display devices for detecting user-intended touch input.

2. Description of Related Art

Touch screens are touch sensitive display devices that act as both aninput device and an output device by incorporating a computer displaywith a sensor such that information may be displayed and received on thesame screen. Touch screens are commonly incorporated into generalpurpose computers, computer terminals, electronic and computerizedappliances, computerized kiosks, personal digital assistants (PDAs),smart phones, and other portable electronic devices. Touch screens areparticularly suited for devices where portability, simplicity, and/ordurability are important.

There are a number of different types of touch screen technologies.Example touch screens include, but are not limited to, resistive,surface acoustic wave, capacitive, infrared, optical imaging, dispersivesignal, and acoustic pulse touch screens. Typically, touch screendevices will detect a touch event, determine coordinates of the touchevent on the screen, and report the coordinates to an operating system(OS) by a suitable data communications technique. In an example, thecoordinates may be reported to a user interface manager or othersuitable application residing on a computing device.

In some instances, unintentional touches may be detected by the touchscreen and reported as a touch event. For example, clothing articles,jewelry, keys, water droplets, or insects may cause a touch event suchthat an unintentional touch event and coordinates are reported. Touchesby such objects may meet criteria for a touch event, but they were notintended touches by the user. Although these conditions may beinfrequent, they may be annoying to a user and counterproductive. For atleast this reason, it is desired to provide improved techniques foraccurately recognizing touch intended by a user of a touch screendisplay device.

BRIEF SUMMARY

In accordance with one or more embodiments of the present invention,display devices and methods for detecting user-intended touch input areprovided. An example display device includes a touch-sensitive displayhaving a suitable touch screen technology. Further, the display deviceincludes an impact sensor attached to the touch-sensitive display andconfigured to generate a signal representative of impact to thetouch-sensitive display. The display device also includes a computingdevice configured to receive the signal. The computing device is alsoconfigured to detect a peak value of the signal. Further, the computingdevice is configured to determine whether a rising edge of the magnitudeof the peak detected signal meets predetermined criteria. The computingdevice is also configured to indicate detection of user-intended touchin response to determining that the predetermined criteria are met.

In accordance with one or more embodiments of the present invention, anexample method includes generating a signal representative of an impactto a touch-sensitive display. The method also includes detecting a peakvalue of the signal. Further, the method includes determining whether arising edge of the magnitude of the peak detected signal meetspredetermined criteria. The method also includes indicating detection ofuser-intended touch in response to determining that the predeterminedcriteria are met.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram of an example display device in accordancewith embodiments of the present invention;

FIG. 2 is a graph of example inputs and a resulting output of anunintentional touch rejection (UTR) gating function in accordance withembodiments of the present invention;

FIG. 3 is a graph of another example of inputs and a resulting output ofa UTR gating function in accordance with embodiments of the presentinvention;

FIG. 4 is a block diagram of an impact sensor and components of acomputing unit in accordance with embodiments of the present invention;

FIG. 5 is a graph showing example outputs of an amplifier and peakdetector shown in FIG. 4 in accordance with embodiments of the presentinvention;

FIG. 6 is a graph showing example outputs of the voltage divider and lowpass filter shown in FIG. 4 in accordance with embodiments of thepresent invention;

FIG. 7 is a schematic of an example unintentional touch rejection systemincluding an impact sensor and a computing unit in accordance withembodiments of the present invention;

FIGS. 8 and 9 illustrate graphs of example signals when a user-intendedtouch event is detected in the presence of various conditions;

FIG. 10 illustrates a graph of the variation in the effective thresholdlevels caused by the noise in accordance with the experiment;

FIG. 11 shows a graph of vibration amplitude versus frequency for bothsystems; and

FIG. 12 illustrates a graph of impact energy versus different ranges.

DETAILED DESCRIPTION

In describing the exemplary embodiments of the present inventionillustrated in the drawings, specific terminology is employed for thesake of clarity. However, the present invention is not intended to belimited to specific terminology so selected, and it is to be understoodthat each specific element includes all technical equivalents whichoperate in a similar manner.

FIG. 1 illustrates a block diagram of an example display device 100 inaccordance with embodiments of the present invention. Referring to FIG.1, the display device 100 includes a display 101 configured to displayimages on a display area. A video controller 103 may receive controlsignaling from an operating system for controlling the display 101 todisplay images. Further, the display device 100 includes a touch sensor102 configured to detect the presence and coordinates of a touch withinthe display area of the display 101. The touch sensor 102 may include atransparent touch surface and may be placed over the display 101 suchthat the user may visually coordinate the touch location with thedisplay images. However, the touch sensor 102 may also be locatedseparately from the display 101 similar to a tablet application. Thedisplay 101 may be, for example, a liquid crystal display (LCD) todisplay images. Alternatively, the display 101 may be any other suitabledisplay technology such as, but not limited to, a cathode ray tube (CRT)monitor, an organic light-emitting diode (OLED) display, or a plasmadisplay panel (PDP). A user of the display device 100 can touch thecorresponding display area of the touch sensor 102 with his or herfinger or other physical device to input a command. Such contact of thedisplay area by the user may be a touch intended by the user anddetected by the touch sensor 102 for inputting a command in accordancewith embodiments of the present disclosure. Various other touches orcontact of the display area of the touch-sensitive display 102 may causeunintended touches to be registered by the touch sensor 102. Suchunintended touches may be ignored by the display device 100 inaccordance with embodiments of the present disclosure.

A transparent plate may be mounted in front of or behind the touchsensor 102 or otherwise an integral part of the touch sensor 102. Thetransparent plate may be, for example, glass, plastic, or crystal. Thetransparent plate may serve to protect the display, for example, whenthe touch screen is used in a public setting or under adverseconditions. Further, the transparent plate may be mounted in such a wayas to allow the plate to vibrate or otherwise move. Accordingly, thetransparent plate may be mounted such that vibrations are not overlydampened.

In an example, a set of x-axis infrared emitters may be mounted abovethe transparent plate. Accordingly, from the perspective of a userfacing the touch sensor 102, the x-axis infrared emitters may occupy aplane closest to the user, the transparent plate may occupy a planebehind the x-axis infrared emitters and the display device may occupy aplane behind the transparent plate. A set of x-axis infrared sensors,corresponding to the x-axis infrared emitters, may be mounted onsubstantially the same plane as the x-axis infrared emitters.Accordingly, light emanating from the x-ray infrared emitters may bedetected by a corresponding x-axis infrared sensor.

Similarly, a set of y-axis infrared emitters may be mounted onsubstantially the same plane as the x-axis emitters and sensors. Acorresponding set of y-axis infrared sensors may be mounted onsubstantially the same plane as the other emitters and sensors.Accordingly, light emanating from the y-axis infrared emitters may bedetected by a corresponding y-axis infrared sensor.

The infrared emitters may include a light emitting diode (LED),incandescent light source, or laser diode emitting light within therange of approximating 750 nm through 1 mm. The emitters may alsoinclude one or more optical lenses that may focus the infrared lightinto a narrow beam.

The infrared sensors may include a photo transistors for detectinginfrared light. The sensors may also include an infrared lens to blockambient light. The infrared sensors may directly correspond to theinfrared emitters. Alternatively, a direct correspondence is notrequired.

When a user of the display device 100 creates a pointing event bytouching a finger or stylus to the transparent plate, infrared light toone or more x-axis sensors and y-axis sensors is blocked. For example,infrared light from a particular x-axis emitter may be blocked fromreaching a corresponding x-axis sensor, and infrared light from aparticular y-axis emitter may be blocked from reaching a correspondingy-axis sensor.

However, there need not be a one-to-one correlation between emitter andsensor. The emitters (or simply one single emitter) may provide a sourceof infrared light that is detected by a set of infrared sensors. Thesensor data may then be analyzed to detect a blocked area where sensedinfrared light is substantially below its unblocked level.Alternatively, the blocking of infrared light caused by the touch eventmay create an interference pattern on the set of sensors that may beinterpreted to localize the touch event. Where only a single infraredemitter is used per axis, the infrared light may be focused into afan-beam shape or repeatedly swept from one side to the other.

An impact sensor 104, for example, a vibration sensor such as apiezoelectric sensor, may be attached to the touch-sensitive display 100and detect an impact to the touch-sensitive display 100. For example,the impact sensor 104 may detect the physical contact of user-intendedtouches of the touch sensor 102, such as when the user intentionallytouches the transparent plate for entering a command or making aselection. The impact sensor 104 may be used in conjunction with thetouch sensor 102 to determine an intentional touch, since an intentionaltouch can cause some small but finite impact energy to a protectiveplate of the display 101. However, the impact sensor 104 may include avibration sensor (e.g., a piezoelectric device) and may therefore alsodetect energies caused by surrounding vibrational noise sources, such ascompressor motors, fans, hard drives, printers, conveyor belts, and thelike. The effect is to negate the effect of determining an intentionaltouch, unless higher thresholds are selected, which in some cases may beuncomfortable or difficult to manage. The presently disclosed inventionprovides equipment and techniques to minimize the effects of vibrationalnoise and therefore increase the accuracy of recognizing intendedtouches by the user of the display 101.

The impact sensor 104 may be mounted in contact with the transparentplate of the display 101 such that the impact associated withuser-intended touch is conducted through the transparent plate to theimpact sensor 104. In this way, the impact sensor 104 may be invibrational communication with the display 101. The impact sensor 104may also be anchored to a relatively stable portion of the display 101.

The impact sensor 104 may be configured to generate a signalrepresentative of an impact to the protective glass of the touch sensor102. For example, a magnitude, frequency, and duration of the signal mayrepresent the characteristic nature of user-intended touch or otherimpact to the protective plate of the touch sensor 102. The signal maybe output to a computing unit 106 configured for detecting user-intendedtouch input in accordance with embodiments of the present invention. Asdescribed in more detail in the examples provided herein, the computingunit 106 may receive the signal from the impact sensor 104 and apply afilter to the signal. The computing unit 106 may also determine whethera rising edge of the magnitude of the filtered signal meet predeterminedcriteria. Further, the computing unit 106 may indicate detection ofuser-intended touch in response to determining that the predeterminedcriteria are met. The computing unit 106 may be implemented by anysuitable combination of hardware, software, and/or firmware.

Indication of detection of user-intended touch may be communicated to atouch controller 108. The touch controller 108 also receives signalsfrom the touch sensor 102 that indicate a coordinate associated with atouch event. For example, the touch sensor 102 in conjunction with thetouch controller 108 may determine a touch event in response to a userintentionally touching the transparent plate to input a command orselection. Further, the touch sensor 102 in conjunction with the touchcontroller 108 may determine a coordinate associated with the touchevent and communicate the touch event and coordinates to the operatingsystem (OS). An unintentional touch event may occur when an unintendedobject comes in contact with the touch sensor 102, such as clothingarticles, jewelry, liquid droplets, insects, and the like may contact.In these instances, the resulting signal characteristics may be similarto intended touches and normal algorithms of the touch controller 108may not distinguish the event from an intended touch by the user, exceptfor assistance provided by the computing unit 106 as disclosed herein.The impact sensor 104 and computing unit 106 provide a secondary sensingsystem. This secondary sensing system provides for concurrent detectionwith the touch sensor 102 and the touch controller 108 such that thecomputing device 106 confirms a user-intended touch before the touchcontroller 108 can report a touch event to an operating system or othercomponent of electronic equipment. If the secondary sensing system isenabled, a touch event detected by the touch sensor 102 that does nothave a corroboration of a concurrent event from the secondary sensingsystem would return to look for other events. That is, with the impactsensor 104, the computing unit 106, and the touch controller 108, anunintentional touch rejection (UTR) feature is provided. The impactsensor 104 and computing unit 106 can determine distinctly differentcharacteristics of a touch event to verify a user-intended touch.

The touch controller 108 includes an unintentional touch rejection (UTR)gating function 110 configured with logic functions for determiningwhether to output a touch event report if the touch event is verified bythe computing unit 106. It is noted that the diagram shown in FIG. 1 isa simplified block diagram of a UTR gating function to pass touch eventsand coordinates to the OS. Typical implementations may be implemented infirmware, not logic hardware. More particularly, the UTR gating function110 may include a logic AND function 112 and a logic OR function 114configured to receive inputs from a touch event manager 116 and thecomputing unit 106. These logical functions may be implemented viahardware logic and/or firmware algorithms. The touch manager 116 mayreceive, from the touch sensor 102, a signal indicating a touch event.In response to receipt of the signal, the touch event manager 116outputs data indicating the touch event and coordinates to an input ofthe AND function 112.

For example, FIG. 2 illustrates a graph of example inputs and aresulting output of a UTR gating function in accordance with embodimentsof the present invention. Referring to FIG. 2, the touch detected signalshows a scenario in which a touch event is detected and an active datasignal is provided as input to the AND function 112. In this example,the touch controller controls data input, here represented by a logicalhigh condition, to the AND function 112 in response to detection of atouch event. Thus, the AND function 112 requires simultaneous input ofanother logic high signal before a touch event can be passed through andreported to the operating system. The other high signal may be providedby suitable signaling of the computing unit 106 in response to verifyingdetection of user-intended touch. When detection by the touch controller108 is complete, the touch controller 108 checks the status of the gatetouch and if present, a touch event and coordinates are sent to theoperating system. Once corroboration of a touch event from the gatetouch signal is made, the touch controller 108 may control operationsbased exclusively on inputs from the touch sensor 102 until the displayindicates that a touch is no longer detected, as indicated by the“REPORTING ENABLED” signal shown in FIG. 2. That is, once a touch isconfirmed, gate touch input from the computing unit 106 is ignored forthat specific touch event and inputs from the touch sensor 102 are usedfor additional coordinate inputs, such as during a “touch-and-drag” userinput, until that specific touch is released, as detected by the touchsensor 102.

The computing unit 106 may receive a signal output from the impactsensor 104 and determine whether the signal meets predetermined criteriafor verifying user-intended touch of the touch sensor 102. The gatetouch output of the computing unit 106 is pulsed high when the computingunit 106 determines that the predetermined criteria are met. Forexample, referring to FIG. 2, the gate touch is pulsed before touchdetection by the touch controller 108. Conversely, the gate touch outputof the computing unit 106 is set low when the computing unit 106determines that the predetermined criteria are not met. The output ofthe computing unit 106 is connected to an input of the OR function 114.The OR function 114 may also receive input from a UTR off function 118for disabling the UTR function by the user via commands sent to thetouch controller 108. Further, the OR function 114 may optionallyreceive input from a UTR enable line 120 for enabling the functionalityof the UTR function when the computing unit 106 is physically present(to allow use of the controller in applications that do not have theimpact detector). Finally, the OR function 114 may receive input fromthe output of the AND function 112 to maintain the output of the OS aslong as there is data from the touch event manager 116.

Once verification is provided by a gate touch input from the computingunit 106, the output to the operating system may be wholly determined bythe touch algorithms of the touch controller 108. That is, anyadditional outputs for change of coordinates would be reported as thoughthe computing unit 106 was disabled until the touch is released asdetected by the touch sensor 102. For example, the UTR function of thecomputing unit 106 is only intended to confirm a touch event, not tocontrol the touch screen function after an initial touch contact. Asshould be appreciated, if a touch event is not confirmed by the gatetouch status, a touch event detected by the touch controller is masked.Further, user input may control whether the UTR function of thecomputing unit 106 is enabled, and a control signal may be provided viathe UTR enable line 120. In an example, the UTR function is disabled bydefault. As an example, FIG. 2. depicts a case where the UTR function isenabled, touch is detected and when the gate touch is high at the sametime, a concurrent condition pulse goes high and enabling a resultingreporting enabled positive condition at the output of the AND function112 when the conditions are met. While the reporting enabled pulse ishigh, touch event data and coordinates from the touch controller 108 arereported to the operating system. When the touch detection condition inFIG. 2 ends, the reporting enabled condition ends and all touch eventand coordinate data is terminated for that particular event.

Criteria for detection of a user-intended touch may be selectivelyadjusted by a user. For example, the touch controller 108 may generateand output a control via sensitivity control signals Sen-A 122 and Sen-B124. A user may input controls via a suitable user application runningin a suitable operating system environment. As an example, the user maycontrol threshold level that a received signal must meet.

A hold time of the gate touch pulse may be set such that the touchcontroller 108 is provided sufficient time to process data from thetouch sensor 102 and to test for a concurrent event. In addition, thegate touch pulse hold time may be set such that its event is coincidentwith the event detected by the touch controller 108. In an example, thehold time may be between about 150 and 200 milliseconds, although anysuitable hold time may be used depending on the time needed by the touchcontroller 108 to process signals.

FIG. 3 illustrates a graph of another example of inputs and a resultingoutput of a UTR gating function in accordance with embodiments of thepresent invention. Referring to FIG. 3, the gate touch pulse is delayedrelative to the touch detected condition that indicates a touch isdetected by the touch controller 108. The touch event report may be helduntil the gate touch status is high, and then the touch controller 108may receive control. As a result, a “hover” time may be provided to auser in which the user's finger or stylus are close enough to thedisplay 101 to be detected by the touch sensor 102 but withoutphysically touching and not causing detection by the impact sensor 104.This feature may allow movement to a target location before contact ismade. In an example, this wait time may be set to about 10 seconds oranother suitable time period. The wait time period may be set by a userby use of a suitable application.

FIG. 4 illustrates a block diagram of the impact sensor 104 andcomponents of the computing unit 106 in accordance with embodiments ofthe present invention. Referring to FIG. 4, the impact sensor 104 inthis example is a piezoelectric sensor, which is in vibrationalcommunication with a touch-sensitive display, such as the display 102.The impact sensor 104 is configured to generate a signal representativeof the touch-sensitive display. An amplifier 400 may receive thegenerated signal, amplify the signal, and output the amplified signal toa peak detector 402. The sample and hold recovery time constant (valueof the resistor Rp times the value of the capacitor Cp). The values maybe configured such that the peak detector 402 filters background noisein the signal and allows sufficiently fast enough recovery to detectrapid multiple touches to the touch-sensitive display. The peak detector402 recovery time may have a time constant of about 3.3 seconds or anyother suitable time constant from less than 0.5 seconds to more than 10seconds. Further, the sample and attack time constant (i.e., charging ofcapacitor Cp) can be set to be fast enough to follow the rise of thetouch impact amplitude.

FIG. 5 illustrates a graph showing example outputs of the amplifier 400and peak detector 402 shown in FIG. 4 in accordance with embodiments ofthe present invention. Referring to FIG. 5, line 500 shows the output ofthe amplifier 400 over time in response to receipt of user-intendedtouch signal of the touch sensor 102. As depicted, a user-intended touchcauses a resonant response similar to a tuning fork, wherein the signalresonates at the natural frequency of the impact sensor 104 (such as 75Hz) and whose amplitude goes from zero to a peak amplitude almostinstantaneously and then decays over time. The presently disclosedsubject matter may be used to recognize such characteristics of thesignal even in noisy vibrational environments. Threshold sensitivitylevels may be set by a user. The peak detector 402 can evaluate theshape of the signal amplitude, not simply its value. Line 502 shows theoutput of the peak detector 402 over time in response to receipt of thesignal depicted by line 500.

The computing unit 106 includes a differential time delay detector 404for detecting user-intended touch signals within a signal generated bythe impact sensor 104. A signal output by the peak detector 402 isreceived by the detector 404 and electrically communicated to twopathways. In one pathway, the peak detector output signal 502 iscommunicated to a voltage divider including resistors Rt1 406 and Rt2408. The voltage divider may generate an output that is a fraction ofthe peak detector output signal 502 and may communicate its output to acomparator 410. The voltage divider provides a threshold effect (Rt1,Rt2). In the other pathway, the peak detector output signal 502 iscommunicated to a low pass filter having a resistor Rd 412 and acapacitor Cd 414. The low pass filter is configured to receive the peakdetector output signal 502 and to apply low pass filtering to the peakdetector output signal 502. The low pass filter communicates its outputsignal to another input of the comparator 410. In this example, thecomparator 410 is an operational amplifier. The comparator 410 canreceive the signals from the voltage divider and the low pass filter asinputs and generate a trigger pulse in response to the output signal ofthe voltage divider being greater than the output signal of the low passfilter. More particularly, the comparator 410 detects when the risingedge of the triangular characteristic signal of a touch event is fastenough and larger than a preset threshold. In this way, the detector 404may determine whether a rising edge and a magnitude of the peak detectoroutput signal 502 meet predetermined criteria for determining a touchevent. In an example, the low pass filter may have a time constant thatis slow enough to detect the rising slope of the triangular waveform. Inanother example, the low pass filter may have a time constant of about10 milliseconds, although it may alternatively be within a range betweenabout 1 and 100 milliseconds.

FIG. 6 illustrates a graph showing example outputs of the voltagedivider and low pass filter shown in FIG. 4 in accordance withembodiments of the present invention. Referring to FIG. 6, line 600shows the output of the voltage divider of the detector 404 in responseto receipt of user-intended touch signal of the touch sensor 102. Line602 shows the output of the low pass filter of the detector 404 inresponse to receipt of user-intended touch signal of the touch sensor102. The comparator 410 compares the two signals and reports auser-intended touch event during the short interval, indicated generallyby reference numeral 604, when the signal output by the voltage divideris greater than the signal output by the low pass filter.

FIG. 7 illustrates a schematic diagram of an example unintentional touchrejection system including an impact sensor 104 and a computing unit 106in accordance with embodiments of the present invention. Referring toFIG. 7, the impact sensor 104 may be attached to a touch-sensitivedisplay and configured to generate a signal representative of impact tothe display. The signal output by the impact sensor 104 may be output toan amplifier 700. The amplifier 700 includes an operational amplifier U1704 configured with components for providing a gain to a signal inputfrom the impact sensor 104. Particularly, the operational amplifier 704is configured with resistors R1 708, R2 710, and R3 712, and a capacitorC1 716 having the shown resistor and capacitance values.

A precision peak detector 720 has an input connected to an output of theamplifier 700. The peak detector 720 includes operational amplifiers U1722 and U2 724, Schottky-type diodes D1 726 and D2 728, resistors R4730, R5 732, R6 734, R7 736, R8 738, and capacitors C2 740 and C3 742.The time constants determined by resistor R7 736, capacitor C3 742, andresistor R8 738 may determine time constants of the detector 720. Thetime constant of resistor R7 736 and capacitor C3 742 may be set to besufficiently short to respond to the rapid rise time of the amplitude ofan impulse signal resulting from user-intended touch. The time constantdefined by resistor R8 738 and capacitor C3 742 may be set to besufficiently long to filter background noise, but short enough torespond to multiple user-intended touches. As a result of such settings,the detector 720 may recover at about the same time as the time neededfor the impulse signal 500 shown in FIG. 5 to completely decay as shownin the example of FIG. 5. It is noted that in the presence of noise, theamplitude of the detector 720 may rise to the same level as the noiseamplitude, but respond equally to an impulse signal. It is also notedthat there may be some “ripple” characteristics to the signal of thedetector 720 that results from noise, but it is minimal.

The system of FIG. 7 includes a differential threshold detector 744having an operational amplifier U4 770, resistors R9 748, R10 750, R11752, and R12 754, and a capacitor C4 756. The detector 744 may alsoinclude a user selectable threshold component 758 having an analogmultiplexer 760 and resistors R13 762, R14 764, R15 766, and R16 768configured for user selection of a threshold level. The input to thedetector 744 from the detector 720 is split into two paths: one to delayand average the signal, referred to as Vavg; and the other to offset thesignal, Voff, by some threshold amount. The Vavg signal is determined bythe resistor R9 748 and the capacitor C4 756 forming a low pass filter.The time constant of the low pass filter may be set such that it is fastenough to recover at the same rate or faster than the peak detector 720,but slow enough to provide some time differentiation from the inputsignal. The Voff signal may respond at the same rate as the peakdetector 720. When there is a sudden increase in the amplitude of thepeak detector 720, there may be a short time period when the Voff signalis greater than the Vavg signal, thus creating a negative pulse on anoutput of an operational amplifier U4 770, which functions as acomparator.

The analog multiplexer 760 may be controlled by input of a user forcontrolling the detection threshold level. For example, the user mayenter a command for controlling the detection threshold level. Inresponse to receipt of the command, control signals may be communicatedvia suitable lines, such as via signals Sen-A 122 and Sen-B 124 shown inFIG. 1. Such signals may be communicated to an input of the analogmultiplexer 760 for controlling the detection threshold level.

The timing difference between the two signals Voff and Vavg is depictedin FIGS. 8 and 9. FIG. 8 illustrates a graph of an example Voff signal800 and Vavg signal 802 when a user-intended touch event is detected andin the presence of little noise. FIG. 9 illustrates a graph of anexample Voff signal 900 and Vavg signal 902 when a user-intended touchevent is detected and during a noisy condition. In FIG. 8, Vavg has aquiescent point of 2.5 volts in this case since there is no or littlenoise. The Voff is offset to a lower quiescent voltage by the thresholdsetting circuits, which include the resistors R10, R12, and R13-R16shown in FIG. 7. The resistor R11 752 functions to maintain a referenceto the Vavg signal. During the lag on the rise of the Voff signal, thereis a short time period of time when it is higher than the Vavg signal.If the offset is increased, the impulse signal must be larger for theVoff signal to cross the threshold of the Vavg signal.

Referring to FIG. 9, noise present on an impact sensor causes the peakdetector voltage to rise and the signals Vavg and Voff to risecorrespondingly as shown. However, the delta is approximately the same,and an impulse can cause approximately the same delta rise between thesignal Voff and the signal Vavg as in the case of no noise as shown inFIG. 9. As a result, noise may be made relatively insignificant to theperformance.

In accordance with one or more other embodiments, an automatic gaincontrol (AGC) feedback from the delay time (C4) Vavg signal to the inputof the amplifier 700 may be provided for extending the operating rangeof vibration noise.

It is noted that FIG. 7 identifies specific component values such asresistor and capacitor values; however, the values of such componentsmay be any other suitable value. For example, the component values mayalternatively be any other suitable value for achieving functionality inaccordance with embodiments of the present invention.

In an experiment, a differential threshold detector was simulated todetermine the effects of background vibrational noise. Several noisefrequencies were tested in the range from 20 Hz to 360 Hz at bothrelatively low noise levels and high noise levels. FIG. 10 illustrates agraph of the variation in the effective threshold levels caused by thenoise in accordance with the experiment. The humanly detectable varianceof +/− dB is shown by the dashed horizontal lines 1000 for reference. Asshown, the variation in the effective threshold is below humanlydetectable levels, and relatively the same independent of backgroundnoise (low or high).

Experiments were conducted to compare the sensitivity to noise for anunintentional touch detection system in accordance with embodiments ofthe present invention to a previous unintentional touch rejectionsystem. The systems were set at a low threshold and the vibration levelwas adjusted until it was observed that touch was detected withoutactually touching a display screen. FIG. 11 shows a graph of vibrationamplitude versus frequency for both systems (it is noted that higher maybe better). The previous unit (designated as UTR) is shown in the graphto be very sensitive to noise in a broad range of frequencies. Incontrast, the unit in accordance with the present invention (designatedas ATUTR, for example) is shown to be more than an order of magnitudeless sensitive.

With the effects that noise may have on the variances of the effectivethreshold, threshold limits may be expanded as shown in FIG. 12, whichillustrates a graph of impact energy versus different ranges. It isnoted that the variance increases upwardly, which is beneficial, andthat the mean does not vary significantly between a quiet and noisyenvironment.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium (including, but not limitedto, non-transitory computer readable storage media). A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the lattersituation scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed:
 1. A display device comprising: a touch-sensitivedisplay; an impact sensor attached to the touch-sensitive display andconfigured to generate a signal representative of impacts to thetouch-sensitive display; and a computing unit configured to: receive thesignal; determine whether a predetermined fraction of the signal isgreater than a low-pass filter output of the signal; and indicatedetection of user-intended touch in response to determining that thepredetermined fraction of the signal is greater than a low-pass filteroutput of the signal, wherein the computing unit is configured to detecta peak value of the signal, and wherein the computing unit comprises: avoltage divider configured to receive the peak detected signal andgenerate a first output that is a fraction of the peak detected signal;a low pass filter configured to receive the peak detected signal and toapply low-pass filtering to the peak detected signal to generate asecond output; and a comparator configured to receive the first andsecond outputs as inputs and to generate a trigger pulse in response tothe first output being greater than the second output to indicatedetection of user-intended touch.
 2. The display device of claim 1,wherein the impact sensor is a piezoelectric sensor.
 3. The displaydevice of claim 1, wherein the impact sensor is in vibrationalcommunication with the touch-sensitive display.
 4. The display device ofclaim 1, wherein the computing unit comprises a peak detector configuredto filter background noise in the signal.
 5. The display device of claim1, wherein the predetermined fraction is defined by a voltage dividerthat is configured to receive the signal as input and to output thepredetermined fraction of the signal.
 6. The display device of claim 1,wherein the low pass filter has a time constant between about 1 and 100milliseconds.
 7. The display device of claim 1, wherein the voltagedivider is configured to selectively adjust a magnitude of the firstoutput to adjust a detection threshold level of detection of theuser-intended touch.
 8. The display device of claim 7, wherein thevoltage divider is configured to receive user input for adjusting thedetection threshold level.
 9. The display device of claim 1, furthercomprising an amplifier configured to receive and amplify the signalfrom the impact sensor.
 10. The display device of claim 1, furthercomprising a touch controller configured to: determine a touch eventassociated with the touch-sensitive display; determine a coordinateassociated with the touch event; determine whether the touch eventoccurs when the predetermined criteria is met; in response todetermining that the touch event occurs when the predetermined criteriais met, communicate the coordinate to a user interface manager.
 11. Thedisplay device of claim 1, wherein the computing unit is configured toindicate that user-intended touch is not detected in response todetermining that the predetermined fraction of the signal is not greaterthan the low-pass filter output of the signal.
 12. A method comprising:generating a signal representative of an impact to a touch-sensitivedisplay; determining whether a predetermined fraction of the signal isgreater than a low-pass filter output of the signal; in response todetermining that the predetermined fraction of the signal is greaterthan a low-pass filter output of the signal, indicating detection ofuser-intended touch; using a voltage divider to receive a peak detectedsignal and to generate a first output that is a fraction of the peakdetected signal; using a low pass filter to receive the peak detectedsignal and to apply low-pass filtering to the peak detected signal togenerate a second output; and generating an indication in response tothe first output being greater than the second output to indicatedetection of user-intended touch.
 13. The method of claim 12, whereingenerating the signal comprises using an impact sensor attached to thetouch-sensitive display to generate the signal.
 14. The method of claim13, wherein the impact sensor is in vibrational communication with thetouch-sensitive display.
 15. The method of claim 12, further comprisingfiltering background noise in the signal.
 16. The method of claim 15,wherein filtering background noise comprises using a peak detector witha recovery time constant between about 0.1 and 10 seconds.
 17. Themethod of claim 12, wherein the low pass filter has a time constantbetween about 1 and 100 milliseconds.
 18. The method of claim 12,further comprising selectively adjusting the voltage divider to adjust amagnitude of the first output to adjust a detection threshold level ofdetection of the user-intended touch.
 19. The method of claim 12,receiving user input for adjusting the detection threshold level. 20.The method of claim 12, further comprising: receiving the signal from animpact sensor attached to the touch-sensitive display; and amplifyingthe signal from the impact sensor.
 21. The method of claim 12, furthercomprising: determining a touch event associated with thetouch-sensitive display; determining a coordinate associated with thetouch event; determining whether the touch event occurs when thepredetermined criteria is met; in response to determining that the touchevent occurs when the predetermined criteria is met, communicating thecoordinate to a user interface manager.
 22. The method of claim 12,further comprising indicating that user-intended touch is not detectedin response to determining that the predetermined fraction of the signalis not greater than the low-pass filter output of the signal.